Ellee Motion SA and Prof. Jean-François Rubin's research group have been working on a recycling chain for waterweed cutting waste, in particular to produce hydrogen. To be able to envisage interesting energy production, they quickly realised that quantities of macrophytes (aquatic plants) would have to be much greater than what local authorities cut down in harbours, around landing stages and in bathing areas. However, given that macrophytes play a key role in lake ecosystems, it is unthinkable to harvest more in natural environments.
Prof. Rubin has therefore come up with a strategy for growing more macrophytes without having to touch the natural seagrass beds. The idea is to grow these aquatic plants on submerged platforms, the depth of which can be varied to allow maximum exposure to sunlight.
The Automatics and Robotics research group was therefore contacted to develop a prototype platform of around 2 m2 that can accommodate substrates with the aim of carrying out studies on the cultivation of macrophytes on a non-natural substrate. Ultimately, if it proves possible to grow significant quantities of biomass on this type of installation, cultivation platforms could be set up where plants do not normally grow, in particular in artificial lakes.
The advantage would be twofold, because not only biomass could be produced, but sites considered sterile could be revitalised, particularly dam lakes where virtually nothing grows because of major changes in water level.
The researchers' initial idea was to be able to adjust the depth of the platform to ensure maximum sunlight. In addition, this adjustment offered the possibility of adapting to major changes in water level (tidal range) without the plants having to suffer the consequences.
An experimental raft was designed by the Automation and Robotics group and installed by Dive Explorer Pro. The immersion depth for the first few months of testing is around 2 m. Various site visits demonstrated the excellent reliability of the device, which resisted the winter conditions perfectly.
It should be noted that although this test platform is currently installed in a natural lake, it is absolutely out of the question to eventually install it in this type of body of water. Artificial lakes are therefore the only possible way forward.
Project partner(s)
Project leader - team
Jeremy Olivier
(HEPIA),
Jean-François Rubin
(HEPIA),
Julien Voëffray
(HEPIA),
Pauline Lourenço
(HEPIA)